Tissue retractor apparatus and methods

ABSTRACT

A delicate tissue retraction system having a hollow tubular retractor, a hollow tubular introducer that is removably installed within the retractor, and a navigation module that is removably installed within the introducer. The navigation module has a shaft with a proximal shaft end and a distal shaft end, and a navigation unit mounted to the proximal shaft end. When assembled, the distal shaft end is contained generally within the introducer and the navigation module outside the introducer. The navigation module indicates the location of one or more points on at least one of the retractor and the introducer to a navigation system.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/674,507, filed Nov. 12, 2012, which is a continuation of U.S.application Ser. No. 13/431,280, filed Mar. 27, 2012, the entirecontents of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to surgical retractor systems, such asbrain retractors, and more specifically to devices that may be used toenhance the functionality of such retractors.

BACKGROUND OF THE INVENTION

A variety of different devices have been used to retract delicate tissueduring surgical procedures. One such device is illustrated in UnitedStates Patent Publication Number 2010/0010315 (“Mangiardi”), to whichthis application claims priority and which is incorporated herein byreference in its entirety. Mangiardi shows two general versions of aretractor for delicate tissue. One version is a closed-channel retractorin the form of a tube (see, e.g., Mangiardi FIG. 3), and the other is anopen-channel retractor in the form of a curved channel (see, e.g.,Mangiardi FIG. 23).

FIG. 1 of this application illustrates a soft tissue retractor systemsuch as found in Mangiardi. The retractor system includes a hollowretractor 100, and an introducer 102 that is selectively inserted intothe retractor 100. The retractor 100 and/or introducer 102 may include ahandle 104 to facilitate manipulation and placement of the retractorsystem, and a lock to hold the introducer and retractor together. Theillustrated handle 104 is molded integrally with the retractor 100, butit may be a separate part. The handle 104 may be configured to connectto a clamp 106, such as the standard surgical clamp 106 shown in FIG. 1.In this example, the handle 104 has a ridge 108 that fits into acorresponding groove 110 on the clamp 106, to prevent relative rotationbetween the two when engaged. Modifications to this design are describedin Mangiardi.

A retractor system such as shown in FIG. 1 is often used by insertingthe introducer 102 into the retractor 100 and locking it in place, sothe two can be moved and manipulated as a unit. The combinedintroducer/retractor system is inserted into the patient's body andmoved to the surgery site, and then the introducer 102 is unlocked andremoved to permit access to the site through the retractor 100. When theunit is in place (either before or after the introducer 102 is removed),the handle 104 may be locked to a clamp 106 to hold the retractor 100 inplace. An example of this procedure is shown in FIGS. 16-20 ofMangiardi. Surgeons using the Mangiardi retractor sometimes do not use aclamp to hold the retractor at the surgery site, and often manuallymanipulate the retractor to access different parts of the surgery siteduring the surgical procedure. The introducer/retractor system and theretractor may be manipulated by holding the proximal ends of theintroducer or retractor or by holding the handle.

The device shown in Mangiardi may have a transparent introducer 102and/or retractor 100, and surgeons using such devices advantageously usethe transparent introducer and retractor to manually guide the unit tothe surgery site. While it has been found that visual guidance bylooking through the introducer 102 is very beneficial, it also has beenfound that some form of additional guidance or navigation may be desiredin some cases. For example, in some cases, surgeons have used a stylet(a narrow elongated rod) to guide the movement of theintroducer/retractor system. In such cases, the stylet is advanced tothe surgery site, and then the interlocked introducer/retractor systemis slid over the stylet until it reaches the surgery site. This isfacilitated by the inclusion of a hole at the tip of the introducer thatfits around the stylet. If the hole through the tip of the introducer isabsent, this method cannot be used.

It has been found that some surgeons using the above procedure may use astylet that is integrated into a computer navigation system. Forexample, the stylet may include a so-called “starburst” or the like, onthe stylet's proximal end (i.e., the end opposite the distal end that isinserted to the surgical site). This and other navigation systems areknown in the art. For example, frameless navigation systems and othercomputerized guidance systems and methods are described in U.S.Publication No. 2001/0027271, and others, and are commercially availablefrom companies such as Medtronic, Inc., Stryker, BrainLab, AG, GeHealthcare. The foregoing reference is incorporated herein by referencein its entirety. As used herein, “computerized guidance” encompasses anymethod of guiding a device to or at a surgical site that relies oncomputer visualization and/or control, as opposed to direct visualinspection and/or manual movement. Mangiardi briefly notes thepossibility of using stereotactic guidance or navigation in conjunctionwith a surgical retractor, but does not illustrate or describe thisprocedure or any apparatus for accomplishing this objective.

While computerized surgical guidance systems are well-known, a number oflimitations exist with respect to their use with introducer/retractorsystems, and particularly with systems like those shown in Mangiardi.For example, while some surgeons use computerized guidance to direct astylet to the surgery site, and then slide the introducer/retractorsystem over the stylet to the site, the movement of theintroducer/retractor may be somewhat imprecise and the process can beunduly cumbersome. This method also is not available if theintroducer/retractor system does not have a through-hole that fits overthe stylet (due either to the absence of a hole or a hole that is toosmall). In addition, the stylet does not provide a view of the tissuethrough which it is advanced, so there is no visual means to perceiveand avoid critical tissue (e.g., major blood vessels or nerves) wheninserting a stylet before inserting a retractor/introducer system. Also,the small-diameter stylet may sever delicate tissue cells, such as greyor white brain matter, rather than moving the cells aside and passingbetween them as would be expected to happen when advancing theintroducer/retractor system.

While preexisting navigation system devices have been used with delicatetissue introducers and retractors, there still exists a need to providealternative solutions. In addition, there is a need to providealternatives to existing systems for manipulating, introducing andholding retractors.

SUMMARY

In one exemplary embodiment, there is provided a delicate tissueretraction system having a hollow tubular retractor, a hollow tubularintroducer, and a navigation module. The retractor has a proximalretractor end and a distal retractor end. The introducer has a proximalintroducer end and a distal introducer end, and the introducer isconfigured to be removably installed within the retractor with theproximal introducer end being adjacent the proximal retractor end andthe distal introducer end extending beyond the distal retractor end. Thenavigation module includes a shaft having a proximal shaft end and adistal shaft end, and a navigation unit mounted to the proximal shaftend. The navigation module being is removably installable within theretractor with the distal shaft end contained generally within theintroducer and the navigation module outside the introducer. Thenavigation module indicates the location of one or more points on atleast one of the retractor and the introducer to a navigation system.

The recitation of this summary of the invention is not intended to limitthe claims of this or any related or unrelated application. Otheraspects, embodiments, modifications to and features of the claimedinvention will be apparent to persons of ordinary skill in view of thedisclosures herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The following Figures are provided to help explain exemplary embodimentsof the invention, but are not intended to limit the claimed invention inany way.

FIG. 1 is an example of a delicate tissue retractor system that may beused with embodiments of the present invention.

FIG. 2 is a cutaway side elevation view of an exemplary retractor systemnavigation module and retractor/introducer system.

FIG. 3 is an isometric view of the exemplary retractor system navigationmodule of FIG. 2.

FIG. 4 is an exemplary embodiment of a tip closure member that may beused with embodiments of introducers having top openings.

FIG. 5 is a cutaway side elevation view of another exemplary retractorsystem navigation module and retractor/introducer system.

FIG. 6 is a cutaway side elevation view of another exemplary retractorsystem navigation module and retractor/introducer system.

FIG. 7 is an isometric view of still another exemplary retractor systemnavigation module and retractor/introducer system.

FIG. 8 is a cutaway side elevation view of the apparatus of FIG. 7.

FIG. 9 is a partial cutaway side elevation view of still anotherexemplary retractor system navigation module and retractor/introducersystem.

FIG. 10 illustrates an exemplary embodiment of an introducer/retractorsystem manipulation arm having a navigation unit.

FIG. 11 illustrates another exemplary embodiment of anintroducer/retractor system manipulation arm that may be equipped with anavigation unit.

FIG. 12 is a cutaway side view of the manipulation arm of FIG. 11.

FIG. 13 is an isometric view of a part of the manipulation arm of FIG.11.

FIG. 14 is an isometric view of another part of the manipulation arm ofFIG. 11.

FIG. 15 is an isometric view of a variation of the manipulation arm ofFIG. 11.

FIG. 16 is an isometric view of another embodiment of anintroducer/retractor system manipulation arm.

FIG. 17 is a partial cutaway side view of the embodiment of FIG. 16.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present disclosure provides exemplary embodiments of variousapparatus that can be used with known or future tissue retractorsystems. Such features include, for example, guidance systems formonitoring and/or controlling the movement of the retractor system and aclamp that can be used to manipulate the system. The features describedherein may be used together or separately, and may be modified asappropriate or desired for the particular application. For illustration,the exemplary embodiments are described herein as they may be adaptedfor use with a soft tissue retractor such as the one shown in FIG. 1. Itwill be apparent to persons of ordinary skill in the art, however, thatother modifications may be made to embodiments used with devices likethe exemplary retractor in FIG. 1, and that other versions may beconstructed for use with other devices that are not similar to thisexemplary embodiment devices.

FIGS. 2 and 3 illustrate a first embodiment of a navigation system thatmay be used with a combined introducer/retractor system. In thisembodiment, the introducer/retractor system comprises a hollow retractor200 into which a hollow introducer 202 is releasably installed. Theintroducer 202 and retractor 200 may comprise structures as described inMangiardi, or have other shapes or configurations. In this example, theintroducer 202 has a tapered proximal end 204, an approximately straightor slightly tapered center portion 206, and a tapered distal end 208that extends beyond the retractor 200 and terminates at a tip 210. Thetip 210 of the introducer 202 has a tip opening 212 that passes throughit. The retractor 200 has a tapered proximal end 214 and a straight orslightly tapered center portion 216, and terminates at the end of thecenter portion 216 at an opening 218. The outer wall of the retractor200 may be chamfered or rounded around the perimeter of the opening 218to help prevent local concentration of pressure when the introducer 202is removed. The retractor 200 and introducer 202 may be a tube (i.e., aclosed channel) having any suitable profile (i.e., shape as viewed alongtheir longitudinal axis 220) that is circular, semicircular,rectilinear, oval, elliptical, or flattened (i.e., provided with onelong dimension and one short dimension) to help prevent unnecessarydisplacement of and pressure on tissue during insertion and use. Theretractor 200 and/or introducer 202 also may have an open channel shape(i.e., non-tubular) having a semicircular profile or other profile. Forexample, the introducer 202 may be tubular with a closed half-circularprofile (such as a “D” shape), and the retractor 200 may be an openchannel with an open half-circular profile (e.g., a “C” shape) thatnests over the introducer profile. The dimensions and shapes of theforegoing features be varied to address different surgical needs.Exemplary dimensions and shapes are provided in the Mangiardi reference.Such devices may be sold in kits that have introducers and retractors ofvarious shapes and/or sizes to provide the surgeon with sufficientvariety to address a number of situations.

The introducer 202 and/or retractor 200 may have transparent wallsthrough which the surgeon can see underlying tissue. For example, thewalls may be made of glass, polycarbonate or other transparent orsemi-transparent materials. While transparent walls are preferred, it isnot required in all embodiments, such as embodiments in which anavigation system supplants the surgeon's reliance on vision to positionthe introducer 202 and retractor 200. The proximal surfaces of theretractor 200 and introducer (222 and 224, respectively) may be treatedto render them non-reflective or glare-resistant, such as by paintingthem matte black or overmolding a matte layer of material. The walls ofthe introducer 202 and/or retractor 200 may also be used as a lightguide to transmit light to the surgical site at the distal end of theretractor 200, as known in the art and shown, for example, in U.S. Pat.No. 3,417,746, which is incorporated by reference herein.

The retractor 200 may include a handle 226 that is shaped and sized tobe retained in a clamp and/or to help a surgeon to manipulate theretractor 200. In this embodiment, the handle 226 includes a raised bead228 that fits into a corresponding groove on a clamp to provide a firmerconnection between the handle and the clamp. Of course, other retentionfeatures may be provided in other embodiments (e.g., the bead may beformed on the clamp, and a corresponding groove formed on the handle226).

A navigation module 230 is selectively installed within the introducer202. In this example, the navigation module 230 may comprise a standardnavigation stylus having a shaft 232 and a navigation unit 250 at theproximal end 236 of the shaft 232. A computer navigation system tracksthe movement of the navigation unit 250 to calculate of the location ofthe distal end 234 of the shaft 232, as known in the art. When installedin the introducer/retractor system, the shaft 232 extends generallyalong the longitudinal axis 220 from the distal shaft end 234 to theproximal shaft end 236. In this embodiment, the distal shaft end 234preferably is located at or near the distal end 208 of the introducer202. Also in this embodiment, the proximal shaft end 236 is locatedoutside and spaced from the proximal introducer surface 222. It isenvisioned that these locations may be modified without departing fromthe general spirit of this disclosure. For example, the proximal shaftend 236 may be located at or even somewhat within the proximalintroducer end 204, provided whatever navigation system is associatedwith the navigation module 230 is still able to operate effectively(e.g., by programming it to associate the displaced tip of the stylusshaft with the actual location of the distal end of the introducer).Infrared or other visual devices might require some part of thenavigation module 230 to be located outside the proximal end 204 of theintroducer 202, but wired electronic systems or navigation units that donot rely on visual contact with a navigation system might be mountedwell within the confines of the introducer 202. While the distal shaftend 234 may, in some embodiments, protrude beyond the distal end 208 ofthe introducer, it is anticipated that locating the distal shaft end 234at or short of the distal end of the introducer 208 may provide aparticular benefit by reducing the likelihood that the distal shaft end234 will interfere with tissue as the system is being advanced throughthe tissue. In this configuration (such as shown in FIG. 2), thenavigation module 230 does not interfere with the benefit of gentletissue separation that is provided by the introducer/retractor system.

The navigation module 230 may be secured to or located within theintroducer 202 by any suitable means. In the embodiment of FIG. 2, thenavigation module 230 is secured by one or more plugs that resilientlyengage the introducer 202. For example, in the shown embodiment, a tipplug 238 is provided at the distal shaft end 234 and a shaft plug 240 isprovided along the shaft 232. The plugs 238, 240 preferably hold thenavigation module in a generally fixed position relative to theintroducer, so that the navigation unit 230 and the introducer/retractorsystem move together as a unit during insertion to the surgery site. Itwill be appreciated that any movement between the navigation module 230and the introducer 202 may cause some inaccuracy in computer navigation,but some minor relative movement may be within operating tolerances.

The plugs 238, 240 preferably are made of a resilient, tactile materialto secure the navigation module 230 to the introducer 202 by frictionalengagement. The plugs 238, 240 may be attached to the shaft 232 eitherpermanently (such as by overmolding) or removably (such as by frictionfitment). One material that is expected to be suitable for the plugs issilicone rubber, but other materials may be used. Using such resilientmaterial, the navigation module 230 can be inserted into the introducer202 and pressed in place with a force to slightly compress the plugs238, 240. The compressed plugs 238, 240 are expected to exert arestoring force against the inner walls of the introducer 202, whichwill hold the navigation module 230 in place until it is removed bypulling it towards the proximal introducer end 204. By connecting thenavigation module 230 to the introducer 202 when the parts are dry, theengagement force can be maximized. However, it is expected thatmaterials such as silicon rubber for the plugs 238, 240 andpolycarbonate for the inner wall of the introducer 202 will maintaingood engagement even in the presence of fluids present during typicalsurgical procedures, and possibly even if the materials are wet whenconnected. In order to minimize the likelihood that fluid will interferewith the connection, features may be provided to address issues that maybe associated with the presence of fluids. For example, one or moregrooves may be provided in the plugs to trap and retain moisture, andthe plugs may have one or more integral wiping features 244 (e.g.,flexible circumferential protrusions) to displace fluid that might bepresent during engagement.

The tip plug 238 and shaft plug 240 may be shaped to conform generallyto the inner walls of the introducer 202. For example, the plugs 238,240 may have an ovate profile if the introducer 202 is ovate, or a roundprofile is the introducer 202 is round. The plugs 238, 240 may betapered or otherwise shaped to correspond to the longitudinal shape ofthe inner wall of the introducer 202. In the embodiment of FIGS. 2 and3, the tip plug 238 includes a circumferential groove 246 thatresiliency engages inside the introducer tip opening 212. Such a tipplug 238 may be shaped and sized to seal the tip opening 212 closedagainst the ingress of fluid. The distal end of the tip plug 238 mayprotrude beyond the end of the tip opening 212, and in that case may beshaped as a tapered or rounded cone 248 to form a smooth contour todisplace tissue as the retractor/introducer unit is advanced to thesurgical site. However, it is not necessary for the tip plug 238 toextend through the tip opening 212 in all embodiments. Indeed, the tipplug 238 may be spaced from the tip opening 212 and from the distal endof the introducer 202. In still other embodiments, the tip plug 238 maybe omitted, and the end of the shaft 232 may be sized to rest againstthe inside wall of the introducer 202 at or around the tip opening 212(if one is present) or the distal end 208 of the introducer 202.

In the embodiment of FIGS. 2 and 3, one or both plugs 238, 240 may beslidable along the shaft 232 to position the plugs 238, 240 to fitinside introducers 202 having different lengths. For example, in theshown embodiment, the shaft plug 240 is shaped as a simple ovate ringthat can be slid in the longitudinal direction 220 along the shaft 232to any desired position. Frictional engagement between the shaft plug240 and the shaft 232 holds the shaft plug 240 in the desired position.If desired, other securements between the shaft plug 240 and the shaft232 may be used, such as radial clamps or the like.

While the foregoing embodiment has been described using resilient plugs238, 240, it will be appreciated that the plugs may be replaced bynon-resilient members, such as solid plastic pieces that are attached toor integrally formed with shaft 232. In such an embodiment, the plugs238, 240 may be used simply to center the navigation module 230 withinthe introducer/retractor system, with a retaining force being providedby the surgeon or other mechanisms. Alternatively, one or both plugs238, 240 may engage portions of the introducer or retractor to hold themtogether. For example, one plug 238 may comprise an exterior thread orbayonet fitting that engages a corresponding thread or bayonet fittingformed on the inner wall of the introducer 202. These and othervariations will be apparent to persons of ordinary skill in the art inview of the present disclosure.

The navigation unit 250 may be attached to the shaft 232, such as bybeing attached at the proximal shaft end 236. The navigation unit 250may comprise any suitable electronic, visual or stereotactic navigationdevice. Examples of such devices include arrangements of LEDs (lightemitting diodes) or “starbursts” comprising multiple optical reflectors,which are used to convey the physical location and orientation of thenavigation unit 250 to an optical detection system set up in theoperation room. Such devices may use visible-light or non-visibleradiation (e.g., infrared light) to detect and track the navigation unit250, as known in the art. Such devices are available from commercialsources, such as Medtronic, Inc., Stryker, BrainLab, AG, Ge Healthcare,and others, and need not be described in detail here. Alternatively, thenavigation unit 250 may be integrally formed with the shaft 232, asknown in the art. Regardless of what kind of navigation unit 250 isused, it may be necessary to program the tracking system with thedimensions of the combined introducer, retractor and navigation unit sothat the program can equate the location of the navigation unit 250 tothe distal end (and perhaps other dimensions) of the introducer 202.Using such programming, the tracking system can know precisely where thetip 210 of the introducer 202 is at all times.

Referring to FIG. 4, it is expected that an embodiment of a device asshown in FIGS. 2 and 3 may be useful even if no navigation unit isprovided. This embodiment is a simple tip closure member 400 having ashaft 402 or other structure to which a tip plug 404 is connected. Theshaft 402 fits within an introducer, such as the introducer 202 shown inFIG. 2, and the tip plug 404 engages and seals the introducer tipopening 212. The shaft 402 preferably is long enough to be accessiblefor removal during surgery, but this is not required. The shaft 402 mayinclude a second plug 406, such as the tapered plug 406 shown in FIG. 4,to help hold the closure member 400 in place, but this is not strictlynecessary. A second plug 406 may be desirable if it is expected thatlateral movement of the shaft 402 within the introducer mightaccidentally dislodge the tip plug 404, however such movement mayactually be desirable to help the surgeon intentionally remove the tipplug 404 when desired.

A device such as the embodiment of FIG. 4 may be useful for surgeonsthat prefer not to have a tip opening 212 formed in the introducer 202.That preference may be due to the expected inflow of fluids into the tipopening 212 during insertion of the introducer/retractor system to thesurgery site, or for other reasons. Regardless of the reason, the tipclosure member 400 is expected to provide an economical way to close andseal an introducer tip opening 212 in introducers that have such anopening.

Referring now to FIG. 5, another embodiment of a navigation module isillustrated and described. This embodiment is used with a retractor 500and introducer 502 similar to the previously-described embodiment. Inthis embodiment, however, the introducer 502 does not include a tipopening, and instead has a closed tip 504. The tip 504 may be formed,for example, as a rounded, tapered cone. Here, the navigation module 506comprises a shaft 508 that is secured to the inner wall 510 of theintroducer 502 by one or more plugs 512, 514, and a navigation unit 516such as described above. The plugs 512, 514 may be constructed asdescribed previously, or have different constructions. For example, thetip plug 512 may be shaped as a generally conical structure instead ofbeing adapted to fit into and seal an introducer tip opening.

It is also envisioned that a navigation module may be provided that fitsintroducer that have tip openings (such as shown in FIG. 2), orintroducers that do not have a tip opening (such as shown in FIG. 5).For example, the tip plug 238 on the navigation module 230 of FIG. 3 maybe shaped to engage the introducer regardless of whether the introducerhas a tip opening or not.

Turning to FIG. 6, another embodiment of a navigation module isillustrated and described. This embodiment mounts to an interconnectedretractor 600 and introducer 602 by installing within the bore of theintroducer 602. In this embodiment, the navigation module 604 comprisesa shaft 606 that engages the introducer, and a navigation unit 614 thatis selectively connectable to the shaft 606. For example, the navigationunit 614 may be selectively mounted in a receptacle 616 at the top ofthe shaft 606. This makes the navigation module 604 a modular system inwhich different navigation units 614 may be selectively fitted todifferent shafts 606 to suit the particular circumstances. For example,a family of different shafts 606 may be provided, each fitting one ormore introducers having different diameters, lengths, profiles or otherdimensions. The receptacle 616 may be a locking cuff, a threadedopening, bayonet fittings, or any other suitable arrangement of engagingparts.

The shaft 606 may be secured to the introducer 602 by one or moreresilient seals 608. The seals 608 may comprise plugs as describedbefore, or other structures. For example, the seals 608 may compriseO-rings or other resilient members that can frictionally engage theintroducer 602. O-rings may be mounted to the shaft by forming acircumferential groove 610 to retain each O-ring. The proximal end 612of the shaft 606 may be flared outward to rest against the end of theintroducer 602, to thereby provide a visual indication when the shaft606 is fully-seated and prevent over-insertion.

In this embodiment the introducer 602 has a tip opening 618, but this isnot required in all embodiments. If a tip opening is provided, it may bedesirable to provide some means to seal the opening, such as a seal thatextends down from the shaft 606. Alternatively, it may be desirable topermit fluid to enter the opening, and to provide some means tofacilitate suction removal of that fluid. For example, a bore may beprovided through the shaft 606 to permit access by a suction tube. Somemeans for providing suction may also be provided in thepreviously-described embodiments. For example, the embodiment of FIGS. 2and 3 may include a notch formed on the upper plug 240 through which asuction tube or other devices can be passed to detect the presence ofand remove fluid.

The foregoing embodiments are illustrated with the navigation modulebeing centered along the longitudinal axis of the introducer. Thisarrangement may be desirable to simplify the spatial relationshipbetween the navigation unit and the end of the introducer, and give thesurgeon a better sense about where the tip of the introducer is locatedduring the surgical procedure. However, this arrangement is notnecessary in all embodiments.

FIGS. 7 and 8 illustrate an embodiment of an offset mount for anavigation module. This embodiment is also shown in relation to a nestedretractor 700 and introducer 702 that are held together with a lock 712.The introducer 702 includes an internal passage 704 that is sized toreceive a shaft 705 of a navigation module 708. As with the otherembodiments, the navigation module 708 includes a navigation unit 710,this time shown as wired unit. The internal passage 704 may be formedintegrally with the introducer using a conventional molding process, butit may alternatively be made separately and attached to the introducer.The internal passage 704 may be closed at the distal end, as shown, orit may be open to facilitate the evacuation of fluid or materialstherefrom.

In the embodiment of FIGS. 7 and 8, the shaft 706 of the navigationmodule 708 may be somewhat loosely retained in the passage 704 byforming them with close tolerances, but not so close that there issubstantial friction upon insertion or removal. In this case, thenavigation module 708 may be held in place manually by the user, bygravity, or simply by contact between the parts. When the most accuratecomputer navigation is desired, it may be recommended to the user toapply a slight retaining force to hold the navigation module 708 snuglyin place in the passage 704. Alternatively, the navigation module may befrictionally retained or locked in place by any suitable arrangement ofdevices. For example, plugs, threads, bayonet fittings, or seals may beprovided to hold the navigation module 708 in place.

One beneficial feature of this embodiment is that the navigation module708 is offset from the centerline of the introducer 702, and thereforeinterferes to a lesser degree (if at all) with the surgeon's view intothe introducer. This feature makes embodiments such as this one suitablefor simultaneous computer (e.g., stereotactic) and manual navigation,thus providing the benefits of both forms of navigation.

Embodiments such as this also may permit access by one or more surgicalinstruments without having to remove the navigation module. This may beparticularly advantageous where a surgeon desires to suction fluid, orto cauterize, cut or remove tissue, during the insertion process or atany other time before the introducer is removed from the retractor. Ofcourse, as with other embodiments described herein, the navigationmodule may be removed at any time to permit operations through theintroducer (or to further enhance the user's view), and then replaced ifdesired.

It will be appreciated that the passage 704 that holds the navigationmodule 708 may be moved to other locations and formed in any suitableway. For example, the passage 704 may be moved to the side of theintroducer 702 that is opposite the handle 720 on the retractor 700, orat other locations around the introducer 702. The passage 704 also maybe formed in the wall of the retractor 700 instead of the introducer702. These and other variations will be apparent to persons of ordinaryskill in the art in view of the present disclosure.

The foregoing exemplary embodiments have generally illustrated anavigation module that is retained in the introducer either loosely orby friction fitment between parts. FIG. 9 illustrates an example of anembodiment in which a navigation module 900 is connected to anintroducer 902 (which is received in a retractor 904) by a mechanicallock 906. The lock 906 comprises an arm 908 having two resilient tabs910. The tabs 910 each have a protrusion 912 that fits into acorresponding detent 914 on the inner wall of the introducer 902. Thearm 906 rests on top of a shelf 916 provided on the shaft 918 of thenavigation module 900. The shelf 916, arm 906 and shaft 918 arepositioned to hold the tip of the shaft 918 (not shown) in properregistration with the tip of the introducer 902 (not shown). When thelock 906 is engaged over the shelf 906, the shaft 918 is fully insertedinto the introducer 902, and a navigation unit 920 at the proximal endof the shaft 918 is properly positioned to navigate. The lock 906 may bereleased by squeezing the tabs 910 together to disengage the protrusions912 from the detents 914. It will be appreciated from the foregoing thatany other suitable mechanical lock may be used to hold a navigationmodule in place in an introducer and/or retractor.

It will be appreciated that other mechanisms or parts may be used tohold a navigation module to an introducer/retractor system. For example,the mechanical lock shown in FIG. 9 may be replaced by a different kindof latch system. As another example, the system of FIG. 6 may bemodified by removing the o-rings 608, and adding an expanding grip thata surgeon can selectively extend radially from the navigation moduleshaft 606 to grip the inner walls of the introducer 602.

Another exemplary embodiment is illustrated in FIG. 10. In thisembodiment, an introducer/retractor system 1000 (which may be heldtogether as a unit by a lock 1002), is connected to a manipulation arm1004. The arm 1004 includes a clamp 1006 that is tightened onto theintroducer/retractor system 1000 by turning a knob 1008 that closes theclamp 1006. Any suitable clamping system may be used for thisapplication. Also, while the shown embodiment shows the clamp 1006engaged to a handle 1010 that extends from the retractor portion of theintroducer/retractor system 1000, the clamp 1006 can engage any othersuitable part of the introducer/retractor system 1000. A navigation unit1012 is connected to the manipulation arm 1004, where it can be used tocomputer navigate the introducer/retractor system 1000. The navigationunit 1012 preferably is mounted at a location where it does notinterfere with visualization into the introducer/retractor system 1000,thereby providing the benefits as described above with respect to theembodiment of FIGS. 7 and 8. It also is preferred for the navigationunit 1012 to be mounted where it can properly work with the rest of thenavigation system, such a by being mounted on the top of the arm 1004,or being elevated on a short post. The navigation unit 1012 may beremovable or movable to facilitate manipulation of the arm 1004 andviewing through the introducer/retractor system 1000.

A further embodiment of a manipulator arm is illustrated in FIGS. 11-14.FIG. 11 shows a manipulator arm 1100 that is connected to an elongatedelliptical retractor 1102. The retractor 1102 may be constructed asshown in Mangiardi or have other shapes or features. The arm 1100comprises a first clamp member 1104 and a second clamp member 1106. Thefirst clamp member 1104 has an upper clamp 1108 that fits over a handle1110 that extends from the retractor 1102. The second clamp member 1106has a lower clamp 1112 that fits below the retractor handle 1110. Thehandle 1110 is held between the upper clamp 1108 and lower clamp 1112,and may be retained by a compressive force generated by the clamps 1108,1112.

The handle 1110 and clamp members 1104, 1106 may include features tohelp engage them and hold them together. For example, the upper clamp1108 may include a recess such as groove 1114 that is shaped to receivea corresponding protrusion such as ridge 1116 on the handle 1110. Thegroove 1114 and ridge 1116 may be straight, but may include a bentportion 1118 (FIG. 13) that ensures that the handle 1110 is positionedat a precise location along the groove 1114. The lower surface of theupper clamp 1108 also may have an indentation 1119 (FIG. 13) withsidewalls 1121 that hold the handle 1110 against rotation. The bentportion 1118 of the groove 1114 and the indentation 1119 and sidewalls1121 are examples of registration features that hold the retractor 1102at a fixed location and orientation with respect to the arm 1100. Itwill be appreciated that in other embodiments the shown registrationfeatures may be moved to other locations, transposed, replaced withrecesses and grooves having different shapes, or even omitted. Forexample the groove 1114 may be formed on the handle 1110, and the ridgeformed on the lower clamp 1108. In alternative embodiments, theforegoing registration features may be replaced by any arrangement ofparts that are shaped to align the retractor 1102 at a particularlocation and/or orientation with respect to the arm 1100, however, it isnot strictly necessary for there to be registration features in allembodiments.

The clamp members 1104, 1106 may be slidable with respect to one anotherto selectively grip and release the retractor handle 1110. For example,in the shown embodiment, the first clamp member 1104 includes a flat,straight slide portion 1120 (FIG. 13), and the second clamp member 1106is slidably mounted on the first clamp member 1104 by providing thesecond clamp member 1106 with a pair of rails 1122 (FIG. 14) that wraparound the slide portion 1120. Each rail 1122 includes one or moreinwardly-extending tabs 1124 that are positioned below the slide portion1120 to capture the slide portion 1120 in place between the rails 1122.If desired, the slide portion 1120 may include one or more cutouts 1126that are large enough to permit the tabs 1124 to pass through. When itis desired to disengage the first clamp member 1104 from the secondclamp member 1106 (such as for cleaning), the second clamp member 1106may be slid backwards towards the proximal end of the first clamp member1104 until the tabs 1124 align with the cutouts 1126. At this point, thesecond clamp member can be lifted vertically off of the first clampmember 1106.

As shown in FIG. 11, the clamp members 1104, 1106 may be interleaved.For example, the first clamp member 1104 may have an open channel 1128that receives a narrow portion 1130 of the second clamp member 1106. Thetwo parts can be removed by rotating them relative to one another, butin normal use they cannot disengage. This construction is expected tomake the arm 1100 relatively compact in the lateral direction, promotepart strength, and promote the even application of force across thewidth of the upper clamp 1108 and lower clamp 1112. The open channel1128 and narrow portion 1130 may be shaped to permit movement between anengaged position (FIG. 11) and an open position (FIG. 12), and maypermit further travel to a release position at which point the tabs 1124align with the cutouts 1126 to allow the clamp members 1104, 1106 to bedisassembled.

FIG. 12 is a cross-sectional view of the arm 1100 showing the clampmembers 1104, 1106 in the open position, and illustrating the generalrelationship between the parts. As noted above, the arm 1100 may apply agripping force to hold the retractor 1102. This may be accomplished, forexample, by making the vertical clearance between the bottom of theupper clamp 1108 and the top of the lower clamp 1112 less than thevertical height of the handle 1110. Thus, the act of sliding the lowerclamp 1112 forward forces the upper clamp 1108 and lower clamp 1112apart and generates a restoring force that compresses against and gripsthe handle 1110. To facilitate engagement of the clamps, one or both ofthe clamps 1108 1112 may include a tapered surface 1132 that slidesalong the handle 1110 like a wedge to slowly increase the restoringforce applied to the handle.

Also, as shown by one example in FIG. 12, the arm 1100 may include aposition lock 1134 that selectively holds the first and second clampmembers 1104, 1106 at particular locations with respect to one another.In this example, the position lock 134 comprises a button 1136 (alsoshown in FIG. 11) that extends through a corresponding countersunk hole1138 (FIG. 14) through the second clamp member 1106. The countersunkhole 1138 has a larger bore adjacent the top surface of the second clampmember 1106, and smaller bore adjacent the lower surface, and is sizedso that the button can slide within the larger bore, but can not passthrough the smaller bore. The button 1136 has a threaded bore, and alocking pin 1140 extends up through the smaller portion of thecountersunk hole 1138 and into the threaded bore. The locking pin 1140has a head located below the lower surfaced of the second clamp member1106. When the locking pin 1140 is threaded into the bore, the pin 1140and button 1136 are captured on the second clamp member 1106. A spring1142 is provided in the countersunk hole 1138 to bias the button 1136and pin 1140 upwards.

When the first and second clamp members 1104, 1106 are connected to oneanother, the head of the locking pin 1140 may be positioned within oneof multiple recesses in a channel 1144 formed in the first clamp member1104. The channel 1144 may include a first recess 1146 located where thehead of the locking pin 1144 rests when the arm 1100 is in the clampedposition (FIG. 11), and a second recess 1148 where the head of thelocking pin 1144 rests when the arm 1100 is in the open position (FIG.12). The channel 1144 also may include a third recess 1150 where thehead of the locking pin 1140 can rest when the first and second clampmembers 1104, 1106 are slid into a release position to disengage themfrom one another (e.g., when the tabs 1124 are aligned with the cutouts1126). The channel 1144 itself is narrower than the recesses, but wideenough that the locking pin 1140 can slide along it when it is depressedby pushing down on the button 1136. While this arrangement may bepreferred in some embodiments, it is not strictly required in all. Otherslide locks or locking mechanisms may be used in other embodiments, if alock is desired. Where no lock is desired, the first and second clampmembers 1104, 1106 may simply be retained by the surgeon's hand orfriction.

Referring still to FIG. 11, a navigation unit 1152 may be mounted on themanipulation arm 1100, much like the arm shown in FIG. 10. In thisembodiment, it may be useful to locate the navigation unit 1152 remotelyfrom the retractor 1102, to permit a surgeon to grip the arm 1100between the navigation unit 1152 and the retractor 1102. This locationmay provide enhanced feel and control during insertion and manipulation,and may inhibit the surgeon's view even less than the embodiments shownpreviously herein.

FIG. 15 shows a variation on the embodiment of FIGS. 11-14. In thisembodiment, the lower clamp 1112 is provided with side walls 1500 thatfit around either side of the upper clamp 1108. The sidewalls 1500prevent or inhibit relative movement in the lateral direction betweenthe lower clamp 1112 and the upper clamp 1108, which enhances thestability and strength of the system. In alternative embodiments, thesidewalls could be placed on the upper clamp 1108 to surround the sidesof the lower clamp 1112, or replaced by a guide pin or rail locatedelsewhere (e.g., a guide rail along the centerline of the parts). Othervariations will be readily apparent to persons of ordinary skill in theart in view of the present disclosure.

FIGS. 16 and 17 show isometric and partially cutaway side views,respectively, of another embodiment of a manipulation arm 1600. Theembodiment is shown in use with an interleaved introducer 1602 andretractor 1604, which may be temporarily connected to one another toform a combined introducer/retractor system. The exemplary introducer1602 is shown with a navigation module 1604 mounted to it, but this isnot required. As with prior embodiments, the manipulation arm 1600 maybe provided with a navigation unit that is connected to the arm 1600itself, and need not be used with navigation system at all (i.e., it maybe used solely for visual or manual navigation. The manipulation arm1600 also may be adapted for use with retractors having different shapesand sizes.

The manipulation arm 1600 includes a handle 1606 and a retractor mount1608 that may be connected by universal joint, such as a spherical balljoint 1610. The ball joint 1610 permits the retractor mount 1608 topivot relative to the handle 1606 around one or more axes (three axes ormovement capability are provided in the shown embodiment). Any suitableuniversal or ball joint construction may be used. For example, the balljoint 1610 may comprise a generally spherical ball 1612 that fits in ahousing 1614 having a corresponding spherical interior space. Thehousing 1614 has an opening through which a handle connector 1616extends to rigidly join the handle 1606 to the ball 1612. The shape andsize of the opening and the handle connector 1616 may generally dictatethe range of movement of the ball 1612 within the housing 1614. Thehousing 1614 itself may be formed by two halves that are held togetherto capture the ball 1612 in place, or it may have sufficient flexibilityto allow the ball 1612 to be snapped into the spherical interior space.A lining, such as a low-friction polytetrafluoroethylene (e.g. Teflon™)material, may be provided in the spherical interior space, to hold theball 1612 firmly. If desired, a clamp (not shown) may be provided tocontrol the friction between the ball 1612 and the housing 1614 or tolock the two together. A clamp may include, for example, a simplethreaded screw that threads into the housing 1614 at a location wherethe screw can be tightened to press the ball 1612 into place within thehousing 1614, or a clamp similar to the rotation lock discussed below.

The manipulation arm 1600 also may include a rotating ring mount 1618.The ring mount 1618 includes an inner ring 1620 and an outer ring 1622that are nested together, with the inner ring 1620 captured in placewithin a track 1624 on the inner surface of the outer ring 1622. Thetrack 1624 holds the inner ring 1620 in the same plane as the outer ring1622, but permits the inner ring 1620 to rotate within the plane as theouter ring 1622. A low-friction liner material may be used to facilitatesmooth movement between the inner and outer rings 1620, 1622. The innerring 1620 includes a through-hole 1626 that is shaped to receive theretractor 1604 portion of the introducer/retractor system. Thethrough-hole 1626 may be shaped to conform to the outer wall of theretractor 1604, and may be formed of a high-friction material to helpgrip and hold the retractor 1604. If desired, a rotation lock 1628 maybe provided to increase friction between the inner and outer rings 1620,1622, or stop relative rotation entirely. For example, the rotation lock1628 may comprise a threaded screw that can be tightened to open orclose a channel 1630 formed in the outer ring 1622, thereby increasingor decreasing the tolerance between the outer ring 1622 and the innerring 1620.

From the foregoing, it will be seen that the embodiment of FIGS. 16 and17 provides two unique benefits. First, the universal joint permits thehandle to be oriented at various angles relative to the retractor mount,and therefore at various angles to the introducer/retractor system. Thisallows use where clearance may be an issue, allows the surgeon to holdthe device more comfortably, and permits connection to a mounting clampat different angles. Where a navigation unit is provided on the handle,this flexibility also may permit the handle to be repositioned toreceive a navigation signal (although movement mid-surgery may requirerecalibration of the navigation unit to continue tracking the relevantparts of the introducer/retractor system). The rotating ring mount alsoenhances the flexibility of the device, by letting the surgeon rotatethe introducer/retractor system with one hand, while it issimultaneously being held by the handle. This arrangement isparticularly helpful where the surgeon is holding the handle (as opposedto it being mounted by a fixed a clamp), and where theintroducer/retractor system is oval instead of round. For ovalretractors, rotation may give enhanced 360° viewing and possibly otherbenefits.

As noted above, any number of navigation systems may be used withembodiments of the invention. Such devices typically operate byassociating a navigation unit with a point in space (the “navigationpoint”). In more sophisticated systems, the navigation unit may beassociated with a multitude of points or geometric shapes. For example,a stylet-type navigation module may associate a navigation unit (such asa series of reflective balls) at one end of the stylet with a singlenavigation point at the other end of the stylet, and it may furtherassociated the navigation unit with the full shape of the stylet. Whenthe computer detects the location and orientation of the navigationunit, it can calculate the location of the navigation point, or even theentire stylet. In the foregoing embodiments, it may be necessary toprogram the computer navigation system to associate the navigation unitwith a navigation point or points on the introducer and/or retractor, orwith some other point as desired. For example, in the embodiment ofFIGS. 7 and 8, the navigation module 708 may be pre-programmed toassociate the location of the navigation unit 710 with the location ofthe tip 714 of the shaft 706. In this case, it may be necessary ordesirable to reprogram this particular navigation module 708 toassociate the location of the navigation unit 710 with the location ofthe tip 716 of the introducer or with other points. If that is the case,then it may be further necessary to prevent the navigation module 708from rotating relative to the introducer 702, as such rotation mightmove the location of the virtual navigation point, for example, rotatingthe navigation module 180 degrees might relocate the associatednavigation point to a location 718 that is offset 180 degrees about theaxis of the shaft 706 from the tip 716 of the introducer 702.

Such concerns may not be present in devices such as the one shown inFIGS. 2 through 6 and 9, because the tip of the introducer in each ofthose embodiments is located along the axis of the navigation module. Inthose cases, however, it may still be necessary or desirable toreprogram the navigation module to account for any difference indistance from the tip of the introducer to the tip of the navigationmodule. To even further reduce the need to reprogram a pre-existingnavigation module such as a navigation stylet, the introducer may beshaped to receive the tip of the navigation stylet at the distal end ortip opening of the introducer, so that no reprogramming is required. Forexample, the tip opening may have a conical shape to receive a conicalnavigation stylet tip.

The foregoing considerations generally relate to navigation modules thathave a pre-programmed virtual association point. Some navigation units,such as the unit shown in FIG. 10, may not be pre-programmed. Such unitsmay be affixed to the introducer/retractor and programmed on acase-by-case basis with any necessary offset to locate the desirednavigation point or points with the orientation and location of thenavigation unit. Such programming may be accomplished, for example, byattaching the introducer/retractor system 1000 and navigation unit 1012to the manipulation arm 1004, locating the tip of the introducer at aknown location, and registering the position of the navigation unit 1012while the introducer is so positioned, to thereby associate the locationof the navigation unit 1012 with that known location. Thereafter,wherever the assembly is moved, the navigation system will register thelocation of the navigation unit 1012 with the position of the tip of theintroducer (assuming the parts are not moved relative to one another).Also, while the foregoing examples may use the tip of the introducer asa navigation point, this is not necessary in all cases.

It is also noted that various foregoing embodiments are shown being usedin relation with an introducer portion of a combined nestedintroducer/retractor system. However, the inventors further envisionthat a navigation module such as described above could be adapted to fitinto a retractor that does not have an introducer. FIG. 11 provides onesuch example. This arrangement may be useful to continue to navigate aretractor after it has been inserted into the patient and the introducerhas been removed. Such an embodiment also may be useful to monitor thelocation of navigation points on the retractor to track any movementthat might occur during the course of an operation. A navigation systemmay be programmed to raise an alarm if the retractor moves by anexcessive amount or towards a predetermined prohibited location.

It is also envisioned that a navigation system may be programmed toassociate with two different points, such as the distal tip of theintroducer and the distal end of the retractor. During introduction, thenavigation system can correlate the position of the navigation unit withthe tip of the introducer. Once the introducer is removed, thenavigation system can then be switched to correlate the position of thenavigation unit with the distal end of the retractor. Other associationsmay also be used, as will be appreciated to persons of ordinary skill inthe art in view of the present disclosure.

It is also envisioned that the navigation module in the foregoingembodiments or other embodiments may, itself, be used as a handle tophysically manipulate the introducer/retractor system. For example, thenavigation module shaft 606 in FIG. 6 may include a manipulation armthat connects directly to the shaft. In such a case, the navigationmodule should be fastened to the introducer or retractor with sufficientretention force to ensure reliable movement together as a unit under theforces being applied to the navigation module. If the retaining forcegenerated by the o-rings in FIG. 6, for example, is not sufficient, asupplemental lock may be provided to hold the navigation module to theintroducer or retractor. For example, the top of the shaft 606 may beconnected to the top of the introducer 602 by threads or othermechanisms to enhance the connection between the parts.

In all of the foregoing embodiments, the navigation module, manipulationarm, tip closure member or other features may be made of materials thatcan either be disposed of after surgery, or reconditioned for later use.For example stainless steel or other materials that can be sterilized(such as by treatment in an autoclave) may be used to form the shaft ofa navigation stylet, or to form the manipulation arms shown in FIGS. 10and 11. While some parts may be reusable, others may be replaceable. Forexample, the shaft in the embodiment of FIG. 6 may be provided as areusable material, and the o-ring seals can be easily removed andreplaced if they become worn out or cannot be sterilized. Alternatively,the shaft in the embodiment of FIG. 6 may be disposable, but a costsavings may be realized by making the navigation unit removable from theshaft and reusable.

The embodiments described herein may be used in any suitable way toprovide the surgeon with computer-assisted navigation or positionalfeedback. These embodiments can provide a particular advantage byconnecting a navigation system to a delicate tissue (e.g., brain)retractor that gently separates and retracts tissue during installationof the retractor while at the same time converting the retractor into apointer for a frameless or computer-based navigation system. Forexample, a navigation system such as described previously herein may beaffixed to a combined introducer/retractor system before surgerycommences, programmed to track one or more navigation points, and theninserted into the patient using stereotactic or other computer-basednavigation. During such use, the navigation module may be periodicallyremoved to provide visual access through the introducer and thenreplaced if desired. Visual access may be possible even with thenavigation module in place, although even in those cases it still may bedesirable to remove the navigation module to provide greater visualaccess or access for surgical instruments. When the introducer andretractor are positioned at the surgery site, the navigation may beremoved in some embodiments for the remainder of the surgery, or it maybe replaced (either with or without the introducer) periodically toadjustment the location of the retractor using computer guidance. Thenavigation module may alternatively remain connected to the retractor atall times. The details of these and other methods will be readilyapparent to persons of ordinary skill in view of the present disclosure.

An example of a surgical procedure using the foregoing embodiments mayinclude a combination of some or all of a number of steps, which may bereordered or repeated as circumstances warrant or by preference of thesurgical team or surgeon. A typical surgical process may begin byanalyzing (e.g., by CAT scan or MRI) a patient's physiology to locate,as precisely as possible, a lesion within the brain tissue or other partof the body. Once the lesion's location is identified, the surgeon plansthe surgical path to the lesion. The surgical path may be conventional,or may take into consideration the unique properties of a retractorsystem such as shown in FIG. 1 to access surgical sites that might nototherwise be operable. Once pre-surgical planning is complete, thepatient is prepared for surgery, an introducer/retractor assembly isequipped with a navigation system, and the navigation system isprogrammed to associate with one or more points on anintroducer/retractor assembly. In a typical brain surgery, the skull isresected to reveal a portion of the dura, which is cut by a minimalincision size to accommodate the introducer and retractor. Thearachnoid, pia mater, grey matter and white matter also may be cut toprovide access for the introducer/retractor system, but some of all ofthese steps may not be necessary in all cases. The introducer/retractorsystem is then inserted into the brain through the cut in the dura, andadvanced forward, using the navigation system to monitor and help makecorrections to the path of the introducer/retractor system. As theintroducer/retractor system is advanced, the navigation module may beremoved periodically to permit visual inspection of the brain tissuethrough the transparent walls (if provided) of the introducer and/orretractor, to permit suctioning of fluid, to relieve pressure, or topermit further incisions through a small opening (if provided) at thetip of the introducer. The navigation module may then be reinserted intothe introducer/retractor, and the assembly advanced further into thebrain. (Of course, tissue other than the brain may be the subject of thesurgical procedure.) The surgeon may also reposition or further advancethe assembly with the navigation module removed. Once theintroducer/retractor system is positioned at the approximate location ofthe lesion, the navigation module may be removed to permit finalpositioning of the system (if necessary), and the introducer may beremoved to provide access to the lesion. Surgical procedures may then beperformed through the introducer, as indicated for the particular lesionand patient conditions.

While the preferred embodiment of the invention has been describedabove, it will be recognized and understood that various modificationsmay be made therein and the appended claims are intended to cover allsuch modifications which may fall within the spirit and scope of theinvention.

I claim:
 1. A delicate tissue retraction system comprising: a retractorcomprising a hollow tubular retractor passage extending along alongitudinal centerline from a proximal retractor end to a distalretractor end; an introducer comprising an introducer passage extendingfrom a proximal introducer end to a distal introducer end, theintroducer being configured to be removably installed within theretractor such that the proximal introducer end and distal introducerend are located along the longitudinal centerline and the distalintroducer end extends beyond the distal retractor end; a navigationmodule comprising a shaft having a proximal shaft end and a distal shaftend, the shaft being configured to removably install within theintroducer passage; and a connector configured to hold the shaft to theintroducer with the shaft spaced from an inner wall of the introducerpassage at the proximal introducer end.
 2. The delicate tissueretraction system of claim 1, wherein, when the introducer is installedwithin the retractor, the proximal introducer end is adjacent theproximal retractor end.
 3. The delicate tissue retraction system ofclaim 1, wherein the introducer passage comprises a hollow tubularintroducer passage.
 4. The delicate tissue retraction system of claim 1,wherein the area of the introducer passage, as measured in a planeperpendicular to the longitudinal centerline, decreases from arelatively large size at the proximal introducer end to a relativelysmall size at the distal introducer end.
 5. The delicate tissueretraction system of claim 1, wherein the introducer passage terminatesat the distal introducer end at a closed tip.
 6. The delicate tissueretraction system of claim 1, wherein the distal introducer endcomprises a tapered, rounded cone.
 7. The delicate tissue retractionsystem of claim 1, wherein the proximal introducer end is larger than atleast a portion of the hollow tubular retractor passage.
 8. The delicatetissue retraction system of claim 1, wherein the distal shaft end isadjacent the distal introducer end when the navigation module isinstalled within the introducer.
 9. The delicate tissue retractionsystem of claim 1, wherein the shaft extends along a centerline of theintroducer passage when the navigation module is installed within theintroducer.
 10. The delicate tissue retraction system of claim 1,wherein the shaft is offset from a centerline of the introducer passagewhen the navigation module is installed within the introducer.
 11. Thedelicate tissue retraction system of claim 1, wherein the distalintroducer end is shaped to receive and hold the distal shaft end on thelongitudinal axis.
 12. The delicate tissue retraction system of claim11, wherein the distal introducer end comprises a closed tip.
 13. Thedelicate tissue retraction system of claim 1, wherein the introducerpassage is open around the shaft.
 14. The delicate tissue retractionsystem of claim 13, wherein the distal introducer end is transparent toallow visualization of underlying tissue therethrough while thenavigation module is installed in the introducer passage.
 15. Thedelicate tissue retraction system of claim 1, wherein the connectorcomprises a plug that engages the inner wall of the introducer passage.16. The delicate tissue retraction system of claim 1, wherein connectorcomprises a mechanical lock.
 17. The delicate tissue retraction systemof claim 16, wherein the mechanical lock is located at the proximalintroducer end.
 18. The delicate tissue retraction system of claim 1,wherein the mechanical lock comprises an arm configured to hold theshaft, the arm having one or more tabs that selectively engage one ormore corresponding detents in the introducer.
 19. The delicate tissueretraction system of claim 1, wherein the navigation module comprises anavigation unit mounted to the proximal shaft end.
 20. The delicatetissue retraction system of claim 19, wherein the navigation unitcomprises one or more reflectors or lights.
 21. The delicate tissueretraction system of claim 19, wherein the distal shaft end is withinthe introducer and the navigation unit is outside the introducer whenthe navigation module is installed within the retractor.
 22. Thedelicate tissue retraction system of claim 1, wherein the navigationmodule is configured to indicate the location of one or more points onat least one of the retractor and the introducer.